The present invention relates to dental impression trays and more in particular to improvements in retention of impression materials in the dental impression trays.
Accurate replication of the teeth and surrounding soft tissues is the primary goal of taking an impression. A dental impression tray should retain the impression material when it is withdrawn from the patient's mouth. If the impression material remains in the mouth when the impression tray is withdrawn, the impression is generally ruined and useless. If the impression material comes loose from any part of the tray, but remains in the tray, the impression will usually be inaccurate. Any flexing or movement of the impression tray during the cure of the impression material generally distorts the impression.
Previously, many mechanical and some adhesive means of retaining the impression material in the impression tray have been employed. Carl Jochum and Harry Schuldt, fathers of three of the inventors, patented the first water-cooled impression tray, U.S. Pat. No. 2,312,171, in 1943. It used a perforated metal liner to retain the impression material. Subsequently, they used a peripheral rim and a horse-shoe shaped wire on the palate area to retain the impression material. These methods work, as is evidenced by the fact the company they founded still manufactures these trays today, but they are expensive and labor intensive to manufacture. To retain the impression material, some dental impression trays use holes, grooves, raised pedestals, serrations, barbs, or grid-like linings. Other impression trays use peel and stick adhesives, adhesive felt-like pads, spray-on adhesives, or brush-on adhesives. These methods work to varying degrees. Some are complex and difficult to manufacture and some require expensive or messy adhesives. The number and scope of the methods employed to retain the impression material in the impression tray proves that until now, retaining the impression material in the dental impression tray has not been easy to accomplish.
It has been known to "sand" blast brass dental impression trays to remove debris and roughness from their surfaces which were residues of manufacture. This was the opposite of the current invention where the sandblasting is not a smoothing procedure because of the manner in which it is carried out, but a rough texturing procedure. The brass offers a harder surface than aluminum and the treatment was with glass beads. The treatment was done by hand aiming straight at the surface to be treated. However, the end surface appearance was satiny, not unlike the matte finish of the aluminum trays of the present invention. In particular because of the straight-on application of the glass beads rather than the tumbling application of the abrasive of the current invention and the hardness of the brass surface as compared to aluminum, the indentations would not, it is believed, be substantively characterizable as undercut. In another brass prior art dental impression tray which had a large rim to retain the dental impression mold, a roughed finish was provided to the inside by sandblasting with a coarse sand the interior surfaces of the tray in the same basically straight-on fashion as described for the glass bead treatment. The roughened finish was macro-visible to the unaided eye in its uneven surface characteristics.
The dental impression tray in perhaps its most classic form is preferably curved sufficient to receive at least a partial arch-shaped group of teeth and channel-shaped in cross-section and wider than the teeth to be received therein. The channel-shaped cross-section provides a recess adapted to hold an approximate predetermined amount of the dental impression material for forming the impression of exposed surfaces of teeth or dental surfaces of the dentition including the surrounding mucosa therein.
The present invention is directed to providing dental impression trays of conventional designs with a microscopicly rough texture to the surfaces that are to be most directly contacted by the dental impression material with a need to retain or hold the dental impression material in positive position after the impression of the dentition has been taken. By microscopic it is meant that the texture is so fine or small that its specific roughening structure cannot be readily distinguished without the use of a microscope. The surface, in its preferred formats will appear matte or dull rather than shiny, smooth and/or polished, but the character of the roughing is indistinguishable as to its detail without microscopic examination. In preferred formats the microscopic rough texture has a substantial occurrence of undercuts in the surface so that the dental impression material is not only retained by normal surface adhesion caused by the increase in surface area but also by being trapped under the undercut overhang.
An object of the invention is to provide a dental impression tray of simple construction adapting it for use with various types of dental impression materials.
Another object is to provide a dental impression tray that provides efficient retention of various dental impression materials.
A further object is to provide a dental impression tray of simple construction with the surface of the handle modified in such a way as to provide a non-slip surface for the gloved hand of a Dentist or Dental Assistant using the dental impression tray.